The invention relates generally to railcars, and more particularly to railcars for shipping automotive vehicles.
For many years, autorack railcars have been used to ship new automotive vehicles from their places of manufacture to distribution centers. Shipping by rail can significantly reduce the cost of shipping such vehicles over long distances as compared with shipping by tractor-trailer.
One factor that limits the number of vehicles that can be shipped on an individual railcar is the height limit imposed on railcars due to the presence of bridges, tunnels and other obstructions over the railways. Another limiting factor is the need to maintain the center of gravity of the loaded railcar at or below a certain height above the top of the rail (ATR) for stability.
While bi-level autorack railcars generally are used to provide adequate clearance to ship certain vehicles such as pick-up trucks, mini-vans and sport utility vehicles, tri-level railcars are typically preferred for shipping passenger cars with lower vertical dimensions. The additional deck enables a larger number of automobiles to be shipped on a single railcar, thus increasing load factor and lowering the cost of transportation.
The mix between shorter height and taller height vehicles being transported in the United States varies depends on multiple ever-changing drivers, e.g., (1) customer demand, (2) the vehicle types being built by specific factories in the U.S. and (3) the mix coming into ports. Having a single rail car that can modified as a response to this ever changing mix in vehicle height would be desirable.
Many tri-level railcars have been constructed by building racks on flat cars. In some cases, the racks may be built on new flat cars that are custom built for auto rack use. In other cases, the racks may be built on flat cars that have been built and used previously for other commercial rail service. In the latter case, the flat cars may exhibit configurational variation as a result of strain incurred while in service. This may impose challenges relating to constructions of the racks, but nevertheless may be more desirable than using new flat cars, for economic and/or environmental reasons. In either case, the deck of the flat car functions as the first deck of the tri-level car, and the second and third decks are supported by the rack. The first, second, and third decks are commonly referred to as the A, B, and C decks respectively.
FIGS. 1 and 2 illustrate a prior art flat car of a type that has been used for auto rack service. The flat car comprises a center sill (a), side sills (b) and A-deck (c). A draft gear housing (d) protrudes above the deck at each end of the railcar. Locations at which auto rack posts are to be attached are indicated at (e).
One of the challenges in adapting flat cars for tri-level auto rack use is that a low flat car deck height has been considered necessary for Cg purposes and overhead clearance purposes, but a low deck height creates bottom clearance issues relative to the draft gear housing (d). The bottom clearance issues have typically been addressed through the use of ramps near the ends of the flat car, as shown schematically for purposes of example in FIG. 3, which raise the deck height near the ends of the flat car. Such ramps enable the flat car deck to have a central low portion along most of its length, providing a sufficiently low Cg for the loaded railcar, while providing adequate bottom clearance for most automotive vehicles to clear the draft gear housing near the ends. In the example shown in FIG. 3, each ramp comprises a generally horizontal raised end section (f) that may be, e.g., about 38 in. ATR, a first sloped section (g) having a horizontal dimension of about 5 ft., a generally horizontal raised intermediate section (h) that has a horizontal dimension of, e.g., about 4 ft. and is lower than section (f) by a height differential (k) which may be, e.g., about 4 to 5 in.; a second sloped section (i), that has a horizontal dimension of about 2 ft., and a generally horizontal center section (j) that is lower than section (h) by a height differential (l) which may be e.g., about 2 in.
The B and C decks are at a generally uniform elevation along the length of the car. The clearance over the A-deck is accordingly greater along the central portion and may be lower by, e.g., 6 to 7 in. along the end portions. The A-deck cannot accommodate certain automobiles with low ground clearance due to the transitions or ramps into and out of the central portion.
While bi-level auto rack railcars in the past have had generally horizontal A-decks, the provision of the low central portion in tri-level auto racks has been considered necessary and important not only from the standpoint of providing adequate clearance, but also from the standpoint of stability, so that the center of gravity of the loaded car is sufficiently low. In some tri-level railcars, at least three vehicles are required to be transported on a low central portion of the A-deck to ensure a sufficiently low center of gravity when the B and C decks are fully loaded.
During loading and unloading of automotive vehicles on the A-deck, sufficient clearance greater than the height of the automotive vehicles must be provided between the uppermost surfaces of the automobiles on the A-deck and the bottom surface of the B-deck to allow for vertical displacement or “bouncing” of the vehicles on their suspension systems as they are driven up and down the ramps near the ends of the A-deck. Tri-level cars have hinged end sections on their B decks that can be raised to provide clearance for automobiles being loaded on the A-deck. The hinged end sections are manually raised and lowered during loading and unloading operations. The hinged end sections must be in their lowered positions to support automobiles thereon.
In tri-level cars heretofore used in commercial rail service, adequate clearance is generally not maintained if the same number of vehicles is loaded on the A-deck as on the B and C-decks, requiring a reduced number of vehicles to be transported on the A-deck. While the B and C-decks can generally accommodate five typical passenger cars each in a conventional tri-level railcar, the A-deck can typically carry only four. The load factor for conventional tri-level railcars is 14 for the majority of passenger cars. Where four vehicles are carried on the A-deck, the automobiles in the end positions typically are inclined due to their location on the ramps.
With conventional tri-level cars, shippers must spend significant amounts of time determining the load makeup of a shipment. Load makeup refers to the specific types of vehicles loaded at specific positions in a railcar. Because conventional tri-level cars have different clearances on different decks and at different positions within individual decks, only specific types of automobiles can be loaded at specific positions. Thus, loading a conventional tri-level car entails locating vehicles that can fit within each position and arranging all of the vehicles on the car to use the available capacity efficiently. In some cases, if no automobiles are being shipped that fit within a particular position, the position remains empty, which can increase the number of railcars required to ship a particular number of automobiles.
As consumers' preferences among different types of automobiles fluctuate due to economic factors such as changes in fuel prices as well as non-economic factors, the mix of automobiles being shipped by rail changes and the demand for various types of vehicle-carrying railcars fluctuates, as do the load makeup decisions. Shipping by rail remains the most cost-efficient method of transporting most vehicles over long distances, and autorack railcar design has improved over the years to enable autorack railcars to transport automobiles more securely and efficiently. However, there remains a need for further improvements in methods for transport of automotive vehicles by rail, and in the auto rack railcars themselves, as well as in methods of manufacturing auto rack railcars.